PRESENTATION

ON

RENEWABLE ENERGY SOURCES IV B.Tech - II SEM

Prepared By:

Dr. P Mallikarjuna Sharma, Professor, EEE

ELECTRICAL AND ELECTRONICS ENGINEERING

INSTITUTE OF AERONAUTICAL ENGINEERING (Autonomous)

DUNDIGAL,HYDERABAD

0

UNIT 1

Principles of Solar Radiation

1

What is Solar Energy?

• Originates with the thermonuclear fusion reactions occurring in the sun.

• Represents the entire electromagnetic radiation (visible light, infrared, ultraviolet, x-rays, and radio waves).

2

Advantages and Disadvantages

• Advantages

• All chemical and radioactive polluting byproducts of the thermonuclear reactions remain behind on the sun, while only pure radiant energy reaches the Earth.

• Energy reaching the earth is incredible. By one calculation, 30 days of sunshine striking the Earth have the energy equivalent of the total of all the planet’s fossil fuels, both used and unused!

• Disadvantages

• Sun does not shine consistently.

• Solar energy is a diffuse source. To harness it, we must concentrate it into an amount and form that we can use, such as heat and electricity.

• Addressed by approaching the problem through:

1) collection, 2) conversion, 3) storage. 3

How much solar energy?

The surface receives about 47% of the total solar energy that

reaches the Earth. Only this amount is usable.

4

Putting Solar Energy to Use: Heating Water

• Two methods of heating water: passive (no moving parts) and active (pumps).

• In both, a flat-plate collector is used to absorb the sun’s energy to heat the water.

• The water circulates throughout the closed system due to convection currents.

• Tanks of hot water are used as storage.

5

Heating Water: Active System

Active System uses antifreeze so that the liquid does not freeze if

outside temp. drops below freezing. 6

Heating Water—Last Thoughts • Efficiency of solar heating system is always less than 100%

because:

• % transmitted depends on angle of incidence,

• Number of glass sheets (single glass sheet transmits 90-95%), and

• Composition of the glass

• Solar water heating saves approx. 1000 megawatts of energy a yr, equivalent to eliminating the emissions from two medium sized coal burning power plants.

• By using solar water heating over gas water heater, a family will save 1200 pounds of pollution each year.

• Market for flat plate collectors grew in 1980s because of increasing fossil fuels prices and federal tax credits. But by 1985, when these credits were removed and fossil fuel prices were low, the demand for flat plate collectors shrunk quickly.

7

Heating Living Spaces

• Best design of a building is for it to act as a solar collector and storage unit. This is achieved through three elements: insulation, collection, and storage.

• Efficient heating starts with proper insulation on external walls, roof, and the floors. The doors, windows, and vents must be designed to minimize heat loss.

• Collection: south-facing windows and appropriate landscaping.

• Storage: Thermal mass—holds heat.

• Water= 62 BTU per cubic foot per degree F.

• Iron=54, Wood (oak) =29, Brick=25, concrete=22, and loose stone=20

8

Heating Living Spaces

Passive Solar

Trombe Wall

Passively heated home

in Colorado

9

Heating Living Spaces

• A passively heated home uses about 60-75% of the solar energy that hits its walls and windows.

• The Center for Renewable Resources estimates that in almost any climate, a well-designed passive solar home can reduce energy bills by 75% with an added construction cost of only 5-10%.

• About 25% of energy is used for water and space heating.

• Major factor discouraging solar heating is low energy prices.

10

Solar-Thermal Electricity: Power Towers

• General idea is to collect the light from many reflectors spread over a large area at one central point to achieve high temperature.

• Example is the 10-MW solar power plant in Barstow, CA.

• 1900 heliostats, each 20 ft by 20 ft

• a central 295 ft tower

• An energy storage system allows it to generate 7 MW of electric power without sunlight.

• Capital cost is greater than coal fired power plant, despite the no cost for fuel, ash disposal, and stack emissions.

• Capital costs are expected to decline as more and more power towers are built with greater technological advances.

• One way to reduce cost is to use the waste steam from the turbine for space heating or other industrial processes.

11

Power Towers

Power tower in Barstow, California 12

Solar-Thermal Electricity: Parabolic Dishes and Troughs

• Focus sunlight on a smaller receiver for each device; the heated liquid drives a steam engine to generate electricity.

• The first of these Solar Electric Generating Stations (SEGS) was installed in CA by an Israeli company, Luz International.

• Output was 13.8 MW; cost was $6,000/peak kW and overall efficiency was 25%.

• Through federal and state tax credits, Luz was able to build more SEGS, and improved reduced costs to $3,000/peak kW and the cost of electricity from 25 cents to 8 cents per kWh, barely more than the cost of nuclear or coal-fired facilities.

• The more recent facilities converted a remarkable 22% of sunlight into electricity.

13

Parabolic Dishes and Troughs

Because they work best under direct sunlight, parabolic dishes

and troughs must be steered throughout the day in the direction

of the sun.

Collectors in southern CA.

14

Direct Conversion into Electricity • Photovoltaic cells are capable of

directly converting sunlight into electricity.

• A simple wafer of silicon with wires attached to the layers. Current is produced based on types of silicon (n- and p-types) used for the layers. Each cell=0.5 volts.

• Battery needed as storage

• No moving partsdo no wear out, but because they are exposed to the weather, their lifespan is about 20 years.

15

Solar Panels in Use

• Because of their current costs, only rural and other customers far away from power lines use solar panels because it is more cost effective than extending power lines.

• Note that utility companies are already purchasing, installing, and maintaining PV-home systems (Idaho Power Co.).

• Largest solar plant in US, sponsored by the DOE, served the Sacramento area, producing 2195 MWh of electric energy, making it cost competitive with fossil fuel plants.

16

Efficiency and Disadvantages

• Efficiency is far lass than the 77% of solar spectrum with usable wavelengths.

• 43% of photon energy is used to warm the crystal.

• Efficiency drops as temperature increases (from 24% at 0°C to 14% at 100°C.)

• Light is reflected off the front face and internal electrical resistance are other factors.

• Overall, the efficiency is about 10-14%.

• Cost of electricity from coal-burning plants is anywhere b/w 8-20 cents/kWh, while photovoltaic power generation is anywhere b/w $0.50-1/kWh.

• Does not reflect the true costs of burning coal and its emissions to the nonpolluting method of the latter.

• Underlying problem is weighing efficiency against cost.

• Crystalline silicon-more efficient, more expensive to manufacture

• Amorphous silicon-half as efficient, less expensive to produce.

17

History of Solar Energy • 1500 BC Egyptian ruler Amenkotep III supposedly had “sounding statues” that emitted a tone when air inside was heated by the sun

• 800 BC Plutarch noted that vestal virgins used metal cones to light ritual fires

• 212 BC Archimedes purportedly used burning mirrors to set fire to ships according to Galen in De Temperamentis (see Mythbusters)

• ~1700 AD French scientist, George Buffon, made multiple flat mirrors to concentrate light to a point. ~1747, he ignited a wood pile 195 ft away (wood ignites at ~250°C with flux of 4.7kW/m2)

• ~1860 Augustin Mouchet built “axicons” (simple cone) to focus on a tube; built steam engines with a 40 ft2 reflector 18

• 1868 John Ericsson built a solar-powered 2.5 HP engine that used a parabolic reflector

• 1878 William Adams built a 2 kW solar water pump near Bombay, India

• 1880 E. Weston suggested a thermocouple for generating electricity

• 1882 Abel Pifre & Mouchot demonstrated a steam engine at Tucleries Garden, Paris, driving a printing press to supply fair visitors with handouts

• 1896 C.G.O. Barr patented an idea to place mirrors on railroad cars, precursor of solar towers

• 1912 Prof. C.V. Boys & Frank Shuman built a 50 HP solar pumping engine at Meadi, Egypt

080130

19

1903 Meadi, Egypt Solar Engine

20

http://www.freeenergynews.com/Directory/Solar/Tesla/Experimentor_1916_Solar_Article.pdf 21

How Much Solar Energy Strikes Earth? • sun gives off 3.90x1026 Watts (Universe 4th edition, p585)

• The earth intercepts energy equal to a disk equal to the

earth’s diameter

• Earth's radius is 3,393,000 meters (WGS84 value is

6,378,137 m/2) Earth's solar interception area is

(3.14)(3,393,000)^2 This equals 3.62x1013 m2

• The amount of power crossing earth's orbit is 1388 watts /

m2 Therefore: the earth intercepts 5.02x1016 watts

• We see that the earth intercepts 50 quadrillion watts of solar

power each day

• We could use some of this energy without depleting the sun!

22

Solar Energy on Earth

• Energy from our sun (1366 W/m^2) is filtered through the atmosphere and is received at the surface at ~1000 watts per square meter or less; average is 345 W/m^2

• Air, clouds, and haze reduce the received surface energy

• Capture is from heat (thermal energy) and by photovoltaic cells yielding direct electrical energy

Solar “constant” varies

1366.1 W/m^2 Atlas 3

1367 W/m^2 NREL

1376 W/m^2 NOAA

1388 W/m^2 NASA 23

Solar Spectrum peaks at ~.5 micron

24

Solar Spectrum changes at surface

25

Radiation paths are critical

Over a year, radiation peaks near the summer solstice. Direct radiation is straight from the sun, while global adds reflected light from the clouds and other objects.

26

Pyranometers measure light intensity

The upper dome contains the incident surface sensor, while the lower sensor measures only indirect light intensity from ground

Sensitivity approximately 70 µV/Wm-²

27

Unit 2

Solar Energy Collection,

Solar Energy Storage and Applications

28

Introduction : For applications such as air conditioning, central power generation, and numerous industrial heat requirements, flat plate collectors generally cannot provide carrier fluids at temperatures sufficiently elevated to be effective. They may be used as first-stage heat input devices; the temperature of the carrier fluid is then boosted by other conventional heating means. Alternatively, more complex and expensive concentrating collectors can be used. These are devices that optically reflect and focus incident solar energy onto a small receiving area. As a result of this concentration, the intensity of the solar energy is magnified, and the temperatures that can be achieved at the receiver (called the "target") can approach several hundred or even several thousand degrees Celsius. The concentrators must move to track the sun if they are to perform effectively.

29

Concentrating collectors

Concentrating, or focusing, collectors intercept direct radiation over a large area and focus it onto a small absorber area. These collectors can provide high temperatures more efficiently than flat-plate collectors, since the absorption surface area is much smaller. However, diffused sky radiation cannot be focused onto the absorber. Most concentrating collectors require mechanical equipment that constantly orients the collectors toward the sun and keeps the absorber at the point of focus. Therefore; there are many types of concentrating collectors .

30

Types of concentrating collectors

• There are four basic types of concentrating collectors:

• Parabolic trough system

• Parabolic dish

• Power tower

• Stationary concentrating collectors

31

Parabolic trough system Parabolic troughs are devices that are shaped like the letter “u”. The troughs concentrate sunlight onto a receiver tube that is positioned along the focal line of the trough. Sometimes a transparent glass tube envelops the receiver tube to reduce heat loss.

32

Parabolic troughs often use single-axis or dual-axis tracking.

33

Temperatures at the receiver can reach 400 °C and produce steam for generating electricity. In California, multi-megawatt power plants were built using parabolic troughs combined with gas turbines.

Parabolic trough combined with gas turbines .

34

Cost projections for trough technology are higher than those for power towers and dish/engine systems due in large part to the lower solar concentration and hence lower temperatures and efficiency.However with long operating experience, continued technology improvements, and operating and maintenance cost reductions, troughs are the least expensive, most reliable solar thermal power production technology for near-term.

35

Parabolic dish systems A parabolic dish collector is similar in appearance to a large satellite dish, but has mirror-like reflectors and an absorber at the focal point. It uses a dual axis sun tracker.

36

A parabolic dish system uses a computer to track the sun and concentrate the sun's rays onto a receiver located at the focal point in front of the dish. In some systems, a heat engine, such as a Stirling engine, is linked to the receiver to generate electricity. Parabolic dish systems can reach 1000 °C at the receiver, and achieve the highest efficiencies for converting solar energy to electricity in the small-power capacity range.

37

Engines currently under consideration include Stirling and Brayton cycle engines. Several prototype dish/engine systems, ranging in size from 7 to 25 kW have been deployed in various locations in the USA. High optical efficiency and low start up losses make dish/engine systems the most efficient of all solar technologies. A Stirling engine/parabolic dish system holds the world’s record for converting sunlight into electricity. In 1984, a 29% net efficiency was measured at Rancho Mirage, California.

38

Power tower system A heliostat uses a field of dual axis sun trackers that direct solar energy to a large absorber located on a tower. To date the only application for the heliostat collector is power generation in a system called the power tower.

39

A power tower has a field of large mirrors that follow the sun's path across the sky. The mirrors concentrate sunlight onto a receiver on top of a high tower. A computer keeps the mirrors aligned so the reflected rays of the sun are always aimed at the receiver, where temperatures well above 1000°C can be reached. High-pressure steam is generated to produce electricity.

40

Stationary concentrating solar collectors

Stationary concentrating collectors use compound parabolic reflectors and flat reflectors for directing solar energy to an accompanying absorber or aperture through a wide acceptance angle. The wide acceptance angle for these reflectors eliminates the need for a sun tracker. This class of collector includes parabolic trough flat plate collectors, flat plate collectors with parabolic boosting reflectors, and solar cooker. Development of the first two collectors has been done in Sweden. Solar cookers are used throughout the world, especially in the developing countries.

41

Working principles of concentrating collectors Unlike solar (photovoltaic) cells, which use light to produce electricity, concentrating solar power systems generate electricity with heat. Concentrating solar collectors use mirrors and lenses to concentrate and focus sunlight onto a thermal receiver, similar to a boiler tube. The receiver absorbs and converts sunlight into heat. The heat is then transported to a steam generator or engine where it is converted into electricity. There are three main types of concentrating solar power systems: parabolic troughs, dish/engine systems, and central receiver systems.

These technologies can be used to generate electricity for a variety of applications, ranging from remote power systems as small as a few kilowatts (kW) up to grid connected applications of 200-350 megawatts (MW) or more. A concentrating solar power system that produces 350 MW of electricity displaces the energy equivalent of 2.3 million barrels of oil.

42

Trough Systems These solar collectors use mirrored parabolic troughs to focus the sun's energy to a fluid-carrying receiver tube located at the focal point of a parabolically curved trough reflector.

43

The energy from the sun sent to the tube heats oil flowing through the tube, and the heat energy is then used to generate electricity in a conventional steam generator. Many troughs placed in parallel rows are called a "collector field." The troughs in the field are all aligned along a north south axis so they can track the sun from east to west during the day, ensuring that the sun is continuously focused on the receiver pipes. Individual trough systems currently can generate about 80 MW of electricity.

44

Trough designs can incorporate thermal storage-setting aside the heat transfer fluid in its hot phase allowing for electricity generation several hours into the evening. Currently, all parabolic trough plants are "hybrids," meaning they use fossil fuels to supplement the solar output during periods of low solar radiation. Typically, a natural gas-fired heat or a gas steam boiler/reheater is used. Troughs also can be integrated with existing coal-fired plants.

45

Dish Systems

Dish systems use dish-shaped parabolic mirrors as reflectors to concentrate and focus the sun's rays onto a receiver, which is mounted above the dish at the dish center. A dish/engine system is a stand alone unit composed primarily of a collector, a receiver, and an engine. It works by collecting and concentrating the sun's energy with a dish shaped surface onto a receiver that absorbs the energy and transfers it to the engine. The engine then converts that energy to heat. The heat is then converted to mechanical power, in a manner similar to conventional engines, by compressing the working fluid when it is cold, heating the compressed working fluid, and then expanding it through a turbine or with a piston to produce mechanical power. An electric generator or alternator converts the mechanical power into electrical power.

46

Each dish produces 5 to 50 kW of electricity and can be used independently or linked together to increase generating capacity. A 250-kW plant composed of ten 25-kW dish/engine systems requires less than an acre of land. Dish/engine systems are not commercially available yet, although ongoing demonstrations indicate good potential. Individual dish/engine systems currently can generate about 25 kW of electricity. More capacity is possible by connecting dishes together. These systems can be combined with natural gas, and the resulting hybrid provides continuous power generation.

Combination of parabolic dish system. 47

Central Receiver Systems Central receivers (or power towers) use thousands of individual sun-tracking mirrors called "heliostats" to reflect solar energy onto a receiver located on top of tall tower. The receiver collects the sun's heat in a heat-transfer fluid (molten salt) that flows through the receiver. The salt's heat energy is then used to make steam to generate electricity in a conventional steam generator, located at the foot of the tower. The molten salt storage system retains heat efficiently, so it can be stored for hours or even days before being used to generate electricit. In this system, molten-salt is pumped from a “cold” tank at 288 deg.C and cycled through the receiver where it is heated to 565 deg.C and returned to a “hot” tank. The hot salt can then be used to generate electricity when needed. Current designs allow storage ranging from 3 to 13 hours.

48

The process of molten salt storage.

shows the process of molten salt storage.

49

Technology Comparison Towers and troughs are best suited for large, grid-connected power projects in the 30-200 MW size, whereas, dish/engine systems are modular and can be used in single dish applications or grouped in dish farms to create larger multi-megawatt projects. Parabolic trough plants are the most mature solar power technology available today and the technology most likely to be used for near-term deployments. Power towers, with low cost and efficient thermal storage, promise to offer dispatchable, high capacity factor, solar-only power plants in the near future.

50

The modular nature of dishes will allow them to be used in smaller, high-value applications. Towers and dishes offer the opportunity to achieve higher solar-to-electric efficiencies and lower cost than parabolic trough plants, but uncertainty remains as to whether these technologies can achieve the necessary capital cost reductions and availability improvements. Parabolic troughs are currently a proven technology primarily waiting for an opportunity to be developed. Power towers require the operability and maintainability of the molten-salt technology to be demonstrated and the development of low cost heliostats. Dish/engine systems require the development of at least one commercial engine and the development of a low cost concentrator.

51

Parabolic Trough Dish/Engine Power Tower

Size 30-320 MW 5-25 kW 10-200 MW

Operating Temperature

(ºC/ºF) 390/734 750/1382 565/1049

Annual Capacity Factor 23-50 % 25 % 20-77 %

Peak Efficiency 20%(d) 29.4%(d) 23%(p)

Net Annual Efficiency 11(d)-16% 12-25%(p) 7(d)-20%

Commercial Status Commercially Scale-up

Prototype Demonstration AvailableDemonstration

Technology

Development Risk Low High Medium

Storage Available Limited Battery Yes

Hybrid Designs Yes Yes Yes

Cost USD/W 2,7-4,0 1,3-12,6 2,5-4,4

(p) = predicted; (d) = demonstrated;

Table Key features of the three solar technologies.

highlights the key features of the three solar technologies.

52

Efficiencies for Converting Solar Radiation to Work

Tmax Topt etamax

100°C 63°C 2.2%

200°C 106°C 4.8%

400°C 179°C 8.5%

800°C 297°C 13.2%

1600°C 480°C 18.4%

Different degrees of concentration . 53

Economic and Environmental

Considerations The most important factor driving the solar energy system design process is whether the energy it produces is economical. Although there are factors other than economics that enter into a decision of when to use solar energy; i.e. no pollution, no greenhouse gas generation, security of the energy resource etc., design decisions are almost exclusively dominated by the ‘levelized energy cost’. This or some similar economic parameter, gives the expected cost of the energy produced by the solar energy system, averaged over the lifetime of the system.

54

Commercial applications from a few kilowatts to hundreds of megawatts are now feasible, and plants totaling 354 MW have been in operation in California since the 1980s. Plants can function in dispatchable, grid-connected markets or in distributed, stand-alone applications. They are suitable for fossil-hybrid operation or can include cost-effective storage to meet dispatchability requirements. They can operate worldwide in regions having high beam-normal insolation, including large areas of the southwestern United States, and Central and South America, Africa, Australia, China, India, the Mediterranean region, and the Middle East, . Commercial solar plants have achieved levelized energy costs of about 12-15¢/kWh, and the potential for cost reduction are expected to ultimately lead to costs as low as 5¢/kWh.

55

Unit 3

Wind Energy and biomass energy

56

Source: Annual Energy Review 1999, U.S. Energy Information Administration. 57

58

Power Class Wind

Power

(W/m2)

Speed

(m/s)

1 <200 <5.6

2 200-

300

5.6-

6.4

3 300-

400

6.4-

7.0

4 400-

500

7.0-

7.5

5 500-

600

7.5-

8.0

6 600-

800

8.0-

8.8

7 >800 >8.8

Wind Power Map of

the USA 59

Wind Energy Projects Throughout the United States of America

Click on the shaded states to access information on existing and planned wind energy projects. Installed MW for each state in black.

Updated:

TOTAL INSTALLED WIND ENERGY CAPACITY: 4,685 MW as of Jan 21, 2003 60

61

U.S. Installed Capacity (Megawatts) 1981-2002

Year MW

1981 10 1982 70 1983 240 1984 597 1985 1,039 1986 1,222 1987 1,356 1988 1,396 1989 1,403 1990 1,525 1991 1,575 1992 1,584 1993 1,617 1994 1,656 1995 1,697 1996 1,698 1997 1,706 1998 1,848 1999 2,511 2000 2,578 2001 4,275

2002 *4,685

62

63

Wind Turbine Power:

P = 0.5 x rho x A x Cp x V3 x Ng x Nb

P = power in watts (746 watts = 1 hp)

rho = air density (about 1.225 kg/m3 at sea level, less higher

up)

A = rotor swept area, exposed to the wind (m2)

Cp = Coefficient of performance (.59 {Betz limit} is the

maximum theoretically possible, .35 for a good design)

V = wind speed in meters/sec (20 mph = 9 m/s)

Ng = generator efficiency (50% for car alternator, 80% or

possibly more for a permanent magnet generator or grid-

connected induction generator)

Nb = gearbox/bearings efficiency (depends, could be as high

as 95% if good)

64

Classes of Wind Power Density at 10 m and 50 m(a)

. 10 m (33 ft) 50 m (164 ft)

Wind

Power

Class

Wind

Power

Density

(W/m2)

Speed(b)

m/s (mph)

Wind

Power

Density

(W/m2)

Speed(b)

m/s (mph)

1 <100 <4.4 (9.8) <200 <5.6 (12.5)

2 100 - 150 4.4 (9.8)/5.1 (11.5) 200 - 300 5.6 (12.5)/6.4 (14.3)

3 150 - 200 5.1 (11.5)/5.6 (12.5) 300 - 400 6.4 (14.3)/7.0 (15.7)

4 200 - 250 5.6 (12.5)/6.0 (13.4) 400 - 500 7.0 (15.7)/7.5 (16.8)

5 250 - 300 6.0 (13.4)/6.4 (14.3) 500 - 600 7.5 (16.8)/8.0 (17.9)

6 300 - 400 6.4 (14.3)/7.0 (15.7) 600 - 800 8.0 (17.9)/8.8 (19.7)

7 >400 >7.0 (15.7) >800 >8.8 (19.7)

65

66

67

68

69

70

71

72

• Environmental benefits

• No emissions

• No fuel needed

• Distributed power

• Remote locations 73

Limitations of Wind Power

Power density is very low. Needs a very large number of wind mills to produce

modest amounts of power.

Cost.

Environmental costs. material and maintenance costs.

Noise, birds and appearance.

Cannot meet large scale and transportation energy needs.

74

Wind Turbine

Noise Levels

75

The Future of Wind Energy

Future of wind energy can be bright if government policies subsidize and encourage its use.

Technology improvements unlikely to have a major impact.

Can become cost competitive for electricity generation if fossil energy costs skyrocket.

76

Biomass Composition of Municipal Solid Waste

Energy Retrieval from Recycling

Incineration and Incinerator Ash

Secure Landfills

Efficiency of Conversion of Sunlight into Biomass

Methane Digesters

Alternative Biomass Fuels for Vehicles

Wood Combustion

Energy Plantations

77

Composition of Urban Garbage

William Rathje

Garbologist

When did Arizona

Residents throw out

the most meat?

78

Composition of Solid Waste

79

Waste Generation Rates over Time

80

Changes in Disposal Methods

81

Energetics of Recycling and Substitution

Energy Cost of Various Materials

Paper Cups 36 Styrofoam Cups 1

Steel from Ore 23 Steel From Scrap 1

Aluminum from Ore 43 Aluminum from Scrap 1

Copper from Ore 4.3 Copper from Scrap 1

Glass from Ore 1.3 Glass from Cullet 1

82

Biodegradability

Biodegradability in garbage dumps: an non-issue.

Rapid biodegradation: requires oxygen and/or water.

Rathje:perfectly preserved years old meat and vegetables!

83

Waste to Energy Plant

Locked into long term contract: may discourage recycling

Fly ash: Bottom ash: Where collected and transported?

84

Metal in Incinerator Ash

Additional concerns: dioxin from burning of chlorine containing

compounds (plastics,etc.). Dioxin: carcinogen, endocrine disrupter

Fly ash: from electrostatic precipitators. Bottom ash: bottom of boiler

Which is most dangerous??

85

Fly Ash Dump in Korba India (from power plant)

No vegetation. 86

Fly Ash Dump in Badarpur, India

Reclaimed using mycorrihizal fungi (bioremediation)

Also small amounts of compost.

Reduces air pollution from fly ash dump. 87

Secure Landfill Black layers on top and bottom: liner

Liner thickness: about 1/3 inch

Circles on bottom: leachate pipes

Note: Gas vent, low permeability soil,

filter layer, barrier layer, drainage layer

88

Percent Trash Disposal in Landfills

89

Biomass Production vs Energy Use

Uses of biomass

Aside from energy?

90

Biomass to Fuel Conversions

Results:

Alcohol (Ethanol)

Biogas (Methane)

Syngas

Gasoline (Biocrude)

Diesel Fuel (Plant Oil)

91

Methods of Biomass to Energy Conversion

Direct combustion

Pyrolysis: thermal decomposition into gas or liquid

Involves high temperatures (500-900°C), low oxygen

Biochemical processes:

Anaerobic digestion by methanogens

Controlled fermentation produces alcohols:

Ethanol (grain alcohol)

Methanol (wood alcohol)

92

Anaerobic Digester

Converts animal or plant waste

Into methane

Typical wastes:

Manure (feed lots,pig farms, poultry)

Olive oil mill waste

Potato processing waste

Big deal: Agricultural Science Depts

93

Optimum Operating Temperature

35°C, maximum liters of methane per day, best retention time?

94

Cellulose High Solids Fermenter

Adjusting agitator shaft of high solids fermenter. Produces methane gas,

high quality compost from sewage sludge, use 1/20th the water

Compared to conventional digesters. Downside: agitator needed. 95

Energy Used to Grow vs Food Energy

Ethanol from corn: 1.74 per gallon to produce vs 95 cents per gallon

Of gasoline.

70% more energy to make ethanol from US corn than energy in ethanol

Good use of ethanol: oxidizer to replace MTBE in gasoline

10% ethanol boosts octane rating of gasoline, replaces lead. 96

Energy Contributions to Bread Loaf Grain production, Baking, Transport, Milling, Shops, Packaging

97

Energy in Biomass

Only a small amount energy in sunlight converted into biomass by plants.

Conversion efficiency varies:

Sugar cane: 2%

Corn: 1%

Typical forest: 0.8%

Most food plants: <0.8%

Maximum theoretical efficiency: 10%

98

Sugar Cane

Sugar cane: very high productivity per acre. Use bagasse

(sugar cane waste) to run boilers to boil sap for sugar.

Bagasse to energy plants: 7% of Hawaiian energy

(Mauritius) 99

Bagasse to Methane Plant: Hilo, HI

100

Plastics Made from Pyrolysis Oil (Wood Chip Waste)

101

Low Cost, Efficient Woodstoves A India, B. Nepal C. Guatemala,

Most of the world cooks with wood. Typical wood stove:

Only 10% efficient. Time to collect wood: 2 to 5 hours per day.

80% of fuel use in developing world; wood for cooking.

Major cause of deforestation, soil erosion.

102

Comparable Efficiency Values

Efficiency: multiply by 100.

103

Rocket Stove vs Three Stone Fire

Rocket Stove: insulated fire box, short chimney, cooks on top of

Chimney, skirt surrounds pot. Built in Guatemala.

104

Rocket Stove

105

Addition of Haybox Haybox: insulated box. Food placed in box and left once water heated

to boiling point. Food continues to cook without fire. (Why?)

106

Air Tight Stove

Stove has lower chamber

With burning wood,

Upper chamber with

Secondary combustion

Long path for exhaust gas

= more complete burning

Note high surface area of

Stove.

About 50% efficient

107

Unit 4

Geothermal Energy and Ocean Energy

108

Geothermal Energy

109

Sources of Earth’s Internal Energy

•70% comes from the decay of radioactive nuclei with long half

lives that are embedded within the Earth

•Some energy is from residual heat left over from Earths formation.

•The rest of the energy comes from meteorite impacts.

110

Different Geothermal Energy Sources

Hot Water Reservoirs: As the name implies these are reservoirs of hot

underground water. There is a large amount of them in the US, but they

are more suited for space heating than for electricity production.

Natural Stem Reservoirs: In this case a hole dug into the ground can

cause steam to come to the surface. This type of resource is rare in the

US.

Geopressured Reservoirs: In this type of reserve, brine completely

saturated with natural gas in stored under pressure from the weight of

overlying rock. This type of resource can be used for both heat and for

natural gas.

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Normal Geothermal Gradient: At any place on the planet, there is a normal

temperature gradient of +300C per km dug into the earth. Therefore, if one

digs 20,000 feet the temperature will be about 1900C above the surface

temperature. This difference will be enough to produce electricity. However,

no useful and economical technology has been developed to extracted this

large source of energy.

Hot Dry Rock: This type of condition exists in 5% of the US. It is similar to

Normal Geothermal Gradient, but the gradient is 400C/km dug underground.

Molten Magma: No technology exists to tap into the heat reserves stored

in magma. The best sources for this in the US are in Alaska and Hawaii.

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Direct uses of geothermal energy is appropriate for sources below 1500C

• space heating

• air conditioning

• industrial processes

• drying

• Greenhouses

• Aguaculture

• hot water

• resorts and pools

• melting snow

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How Direct Uses Work

•Direct Sources function by sending water down a well to be heated by the

Earth’s warmth.

•Then a heat pump is used to take the heat from the underground water to the

substance that heats the house.

• Then after the water it is cooled is injected back into the Earth.

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Ground Heat Collectors This system uses horizontal loops filled with circulating water at a depth of 80

to 160 cm underground.

Borehole Heat Exchange

This type uses one or two underground vertical loops that extend 150

meters below the surface.

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Generation of Electricity is appropriate for sources >150oC

Dry Steam Plants: These were the first type of plants created. They use

underground steam to directly turn the turbines.

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Flash Steam Plants: These are the most common plants. These systems pull

deep, high pressured hot water that reaches temperatures of 3600F or more to

the surface. This water is transported to low pressure chambers, and the

resulting steam drives the turbines. The remaining water and steam are then

injected back into the source from which they were taken.

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Binary Cycle Plants: This system passes moderately hot geothermal water

past a liquid, usually an organic fluid, that has a lower boiling point. The

resulting steam from the organic liquid drives the turbines. This process

does not produce any emissions and the water temperature needed for

the water is lower than that needed in the Flash Steam Plants (2500F –

3600F).

Casa Diablo

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Hot Dry Rocks: The simplest models have one injection well and two

production wells. Pressurized cold water is sent down the injection well

where the hot rocks heat the water up. Then pressurized water of

temperatures greater than 2000F is brought to the surface and passed

near a liquid with a lower boiling temperature, such as an organic liquid

like butane. The ensuing steam turns the turbines. Then, the cool water

is again injected to be heated. This system does not produce any

emissions. US geothermal industries are making plans to commercialize

this new technology.

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Geothermal’s Harmful Effects

Brine can salinate soil if the water is not injected back into the reserve after

the heat is extracted.

• Extracting large amounts of water can cause land subsidence, and this can

lead to an increase in seismic activity. To prevented this the cooled water

must be injected back into the reserve in order to keep the water pressure

constant underground.

• Power plants that do not inject the cooled water back into the ground can

release H2S, the “rotten eggs” gas. This gas can cause problems if large

quantities escape because inhaling too much is fatal.

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•One well “blew its top” 10 years after it was built, and this threw hundreds

of tons of rock, mud and steam into the atmosphere.

•There is the fear of noise pollution during the drilling of wells.

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Geothermal’s Positive Attributes • Useful minerals, such as zinc and silica, can be extracted from underground

water.

• Geothermal energy is “homegrown.” This will create jobs, a better global trading position and less reliance on oil producing countries.

• US geothermal companies have signed $6 billion worth of contracts to build plants in foreign countries in the past couple of years.

• In large plants the cost is 4-8 cents per kilowatt hour. This cost is almost

competitive with conventional energy sources.

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•Geothermal plants can be online 100%-90% of the time. Coal plants can only be

online 75% of the time and nuclear plants can only be online 65% of the time.

•Flash and Dry Steam Power Plants emit 1000x to 2000x less carbon dioxide than

fossil fuel plants, no nitrogen oxides and little SO2.

•Geothermal electric plants production in 13.380 g of Carbon dioxide per kWh,

whereas the CO2 emissions are 453 g/kWh for natural gas, 906g g/kWh for oil and

1042 g/kWh for coal.

•Binary and Hot Dry Rock plants have no gaseous emission at all.

•Geothermal plants do not require a lot of land, 400m2 can produce a gigawatt of

energy over 30 years.

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•Geothermal Heat Pumps:

- produces 4 times the energy that they consume.

-initially costs more to install, but its maintenance cost is 1/3 of the cost

for a typical conventional heating system and it decreases electric bill. This

means that geothermal space heating will save the consumer money.

-can be installed with the help of special programs that offer low

interest rate loans.

•Electricity generated by geothermal plants saves 83.3 million barrels of fuel

each year from being burned world wide. This prevents 40.2 million tons of

CO2 from being emitted into the atmosphere.

•Direct use of geothermal energy prevents 103.6 million barrels of fuel each

year from being burned world wide. This stops 49.6 tons of CO2 from being

emitted into the atmosphere.

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Availability of Geothermal Energy

• On average, the Earth emits 1/16 W/m2. However, this number can be much higher in areas such as regions near volcanoes, hot springs and fumaroles.

• As a rough rule, 1 km3 of hot rock cooled by 1000C will yield 30 MW of electricity over thirty years.

• It is estimated that the world could produce 600,000 EJ over 5 million years.

• There is believed to be enough heat radiating from the center of the Earth to fulfill human energy demands for the remainder of the biosphere’s lifetime.

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Geothermal production of energy is 3rd highest among renewable

energies. It is behind hydro and biomass, but before solar and wind.

Iceland is one of the more countries successful in using geothermal

energy:

-86% of their space heating uses geothermal energy.

-16% of their electricity generation uses geothermal energy.

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World Wide Geothermal Uses and Potential

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Overview of Ocean Energy

-ocean energy is replenished by the sun and through tidal influences of the moon’s and sun’s gravitational forces -near-surface winds induce wave action and cause wind-blown currents at about 3% of the wind speed -tides cause strong currents into and out of coastal basins and rivers

-ocean surface heating by some 70% of the incoming sunlight adds to the surface water thermal energy, causing expansion and flow -wind energy is stronger over the ocean due to less drag, although technically, only seabreezes are from ocean energy

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How much energy and what types? -250 Billion barrels of oil worth of energy coming into ocean every day

-80 million barrels of oil per day produced

kinetic

potential

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-250 Billion barrels of oil worth of energy coming into ocean every day

-80 million barrels of oil per day produced

How much energy and what types?

Theoretical global resource of ocean energy: 8,000-80,000 TWh/yr for wave energy 800 TWh/yr for tidal current energy 2,000 TWh/yr for salinity gradient energy 10,000 TWh/yr for ocean thermal energy

World’s electricity consumption 17,000 TWh/yr

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Source of Ocean Wave Energy

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Wave Energy Extraction Technologies Point

Absorber

(OPT,

Finavera)

Oscillating Water Column (Energetech/Oceanlinx)

Attenuator, Pelamis WP Overtopping, Wave Dragon

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Power From Ocean Waves

kW/m crest length

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Power From Ocean Waves • Wave energy is strongest on the west coasts and increases toward the poles. • At approx. 30 kW/mcl in the Northwest (yearly avg.), a single meter (3.3 feet) of wave has the

raw energy to power about 23 homes.

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Point absorber buoys: most common

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Ocean Power Technology buoy, to best tested this month off Oregon

will power 50 homes. Federal permit obtained for grid-connection.

capacity = 150 kW

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Oscillating Water Column Installations: LAND

NOTE: Plant Bowen (Georgia Power) operates at 3,200,000 kW

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Oscillating Water Column Installations: OCEAN

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“Overtopping” Wave Energy

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“Sea Snake” Wave Energy

121m long, 3.5m tall! 147

Unit 5

Direct Energy Conversion

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Tidal Energy Conversion

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Ocean Renewable Power Company installed first grid-connected tidal

device in Cobbscook Bay, Maine in June, 2012. Powers 25 homes. 150

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Ocean Thermal Energy Conversion

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210 kW OTEC test plant, 1993-1998, Hawaii

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Future OTEC plant: grow food and fuel?

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Ocean Energy: Where are we today?

Wave Energy (grid-connected): -0.4MW and 0.5MW OWC off the coast of Pico and Islay by 2008 -2.25MW Pelamis off Portugal by 2008 -0.5MW section of Wave Star Energy off Denmark by 2009 -7MW Wave Dragon off Wales by 2010

Tidal: - barriers: 240MW France in 1966 and 20MW in Canada -Current: 1.2MW off Ireland by 2009, 1MW France

Thermal: -0.2MW Hawaii 1993-1998

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